- Creatinine clearance or Radioisotope GFR ≥ 70 ml/min/1.73m2 or a serum creatinine based on age as follows: Less than or equal to 5 years of age= Maximum Serum Creatinine (mg/dL)of 0.8; Older than 5 but 10 years or younger= Maximum Serum Creatinine (mg/dL)of 1.0; Older than 10 but 15 years or younger= Maximum Serum Creatinine (mg/dL)of 1.2; Older than 15 years= Maximum Serum Creatinine (mg/dL) of 1.5